1. Field of the Invention
The present invention relates to a clutch that could enhance the performance of the clutch, and more particularly to one that could strengthen the engaging force of each clutch weight to make the power transmission of the clutch more smooth and more stable.
2. Description of the Prior Art
A clutch has been widely used in the automatic transmission mechanism of a vehicle. The function of clutch is to transmit the engine power, clutch weights are pivotally installed on a base plate. When the rotation speed of base plate is increased, the clutch weights will fly outward to grasp the driven member and the power is transmitted to the driven shaft to drive the vehicle; when the rotation speed of base plate is decreased, the clutch weights will move inward then the transmission of power is terminated; In which, both ends of each clutch weight are connected with the tension spring (return element). The timing of opening or closing of clutch weights is determined by the tension strength of the tension springs.
Theoretically, if the tension strength of each tension spring (return element) is identical as required then the movement (i.e., opening/closing) of each clutch weight should be synchronous. But in reality, the throttle is variable all the time so the rotation speed of base plate is not in a constant revolution thus the centrifugal force of each clutch weight will be different due to the revolution of each clutch weight is dissimilar. Then transmission efficiency of clutch becomes unstable and inefficient.
There are many patents which disclose the adjustment and setting of the tension strength of the tension springs, such as European Patent No. EP 1310695 A1, Taiwan Patent Publication No. 382350 titled “Motorcycle Clutch Structure”, Taiwan Patent Publication No. 739262 titled “Motorcycle Automatic Gearshift Clutch”, Taiwan Patent Publication No. 447470 titled “Motorcycle Clutch Structure”, Taiwan Utility Model Registration No. M277835 titled “Motorcycle Clutch Structure”. Basically the technical means of these patents are to change the connecting distance of the tension spring between two clutch weights to adjust the tension force of the tension spring. However, these structures of the aforesaid patents still have the problems that the engaging force is weak and the engagement of the clutch weight is unstable. As shown in FIG. 10 and FIG. 11, PCT Publication No. WO 2010048990 discloses a clutch which comprises a plurality of clutch weight area integrally formed into clutch block 1. Through the flexibility of material used for clutch block 1 and the special designing of clutch weight area in the clutch block 1, thus the flexibility of clutch weight area is inherent without any return element, However, the engaging force is still too weak (clutch slippage is serious), so the transmission efficiency of clutch block 1 is still unstable.